Available on TI-99/4A computers. On the right side
  
    | Pin | Name | Dir | Description | 
  
    | 1 | VCC | - | +5 Volts power supply | 
  
    | 2 | SBE | OUT | Low if addr in >9000-94xx (sound port) | 
  
    | 3 | RESET* | OUT | System reset (active low) | 
  
    | 4 | EXTINT* | IN | External interrupt (active low) | 
  
    | 5 | A5 | OUT | Address bus, bit 5 | 
  
    | 6 | A10 | OUT | - | 
  
    | 7 | A4 | OUT | - | 
  
    | 8 | A11 | OUT | - | 
  
    | 9 | DBIN | OUT | Active high = read memory | 
  
    | 10 | A3 | OUT | - | 
  
    | 11 | A12 | OUT | - | 
  
    | 12 | READY | IN | Active high = memory is ready | 
  
    | 13 | LOAD* | IN | Unmaskable interrupt (=> BLWP @>FFFC) | 
  
    | 14 | A8 | OUT | - | 
  
    | 15 | A13 | OUT | - | 
  
    | 16 | A14 | OUT | - | 
  
    | 17 | A7 | OUT | - | 
  
    | 18 | A9 | OUT | - | 
  
    | 19 | A15 | OUT | Address bus, lsb. Also CRU output bit. | 
  
    | 20 | A2 | OUT | - | 
  
    | 21 | GND | - | Ground | 
  
    | 22 | CRUCLK* | OUT | Inversion of TMS9900 CRUCLOCK pin | 
  
    | 23 | GND | - | Ground | 
  
    | 24 | PHI3* | OUT | Inversion of phase 3 clock | 
  
    | 25 | GND | - | Ground | 
  
    | 26 | WE* | OUT | Write Enable (derived from TMS9900 WE* pin) | 
  
    | 27 | GND | - | Ground | 
  
    | 28 | MBE* | OUT | Active low if addr in >4000-5FFF (card ROMs) | 
  
    | 29 | A6 | OUT | - | 
  
    | 30 | A1 | OUT | - | 
  
    | 31 | A0 | OUT | Address bus, bit 0 (most significant) | 
  
    | 32 | MEMEN* | OUT | Memory access enable (active low) | 
  
    | 33 | CRUIN | IN | CRU input bit to TMS9900 | 
  
    | 34 | D7 | IN/OUT | Data bus, bit 7 (least significant) | 
  
    | 35 | D4 | IN/OUT | - | 
  
    | 36 | D6 | IN/OUT | - | 
  
    | 37 | D0 | IN/OUT | Data bus, bit 0 (most significant) | 
  
    | 38 | D5 | IN/OUT | - | 
  
    | 39 | D2 | IN/OUT | - | 
  
    | 40 | D1 | IN/OUT | - | 
  
    | 41 | IAQ | IN | Interrupt acknowledged by TMS9900 | 
  
    | 42 | D3 | IN/OUT | - | 
  
    | 43 | VDD | - | -5 Volts power supply | 
  
    | 44 | AUDIOIN | IN | To sound generator AUDIO IN pin |